A girl, also 15, has denied murdering the pair at their home in Lincolnshire at Nottingham Crown Court

Elizabeth Edwards (L) and her 13-year-old daughter Katie (R), were found dead in Spalding, LincolnshireFamily handout

A mother and daughter were knifed to death in a "cold, calculated and callous" killing carried out b y two teenagers, a court was told. Two 15-year-olds are accused of murdering Elizabeth Edwards, 49, and her 13-year-old daughter Katie in their beds on 13 April this year.

The pair were found dead in their homes, in Spalding, Lincolnshire, on 15 April and the two suspects, including the boy who was 14 at the time, were arrested afterwards. The boy has pleaded guilty to the double murder at Nottingham Crown Court.

But the girl, 15, denies murder but has admitted manslaughter due to diminished responsibility. The pair cannot be named because of their ages.

Opening the case for the crown, Peter Joyce QC said the pair were stabbed through the throat in their beds at their home. According to the BBC, Joyce said: "The prosecution case is that this girl together with the boy planned and carried out the cold, calculated and callous killings.

"Afterwards there has not been a hint of remorse and the prosecution case is that she is as guilty as the boy of the murders. She is not denying that she was just as involved as [the boy] in being party to the killings, she wanted the killings to happen; [but] she is asserting that her mental condition at the time reduces her responsibility from murder to manslaughter."

Elizabeth, 49, was found after being repeatedly stabbed lying on bed in a room that had "blood spatters" on the wall, floor, and bedding, the court heard. She was stabbed three times in the throat, injuring her jugular vein and almost completely cutting through her windpipe, the prosecution said.

A pathologist said they found eight sharp force injuries of which five were on her hands – suggesting she was trying to fend off the blows.

Her daughter Katie was found lying on a mattress in her bedroom with two stab wounds to her neck which suggested the use of severe force. She had also been smothered with a pillow.

It was stated by the crown that after the killings the two teenagers took a bath together and watched Twilight films.

The bodies of Elizabeth and Katie were found by police on 15 April, four days after the prosecution say the alleged killers began plotting their deaths.

It was also revealed on the first day of the trial that in a police interview, following the discovery of the bodies, the girl told detectives the pair had been planning to take their own lives.